I'm afraid I don't have any good news for you, as this happened to us when we upgraded SharePoint.

Basically K2 stores the InfoPath XML encrypted in their database.  They only get decrypted at runtime.  It's not possible to do a find & replace of all your old server references to your new one.  Even if you change the local XML files, they will get overwritten when the user attempts to open the task again.

The only proposed solution we were provided was to develop a custom listener on the server itself to do the replacement at runtime.  This wasn't feasible or reasonable for us to do.  After months of trying to find a solution we eventually decided to abandon the several hundred workflows and have users resubmit them, unfortunately.

Hi Victoria,

thanks for the information...not that good news :-/

For better understanding (for me): 

I have all InfoPath tasks forms stored in the sharepoint forms library where the infopath form was deployed to.

I can change some XML Values in the form with downloading locally and uploading again. It seem that the tasks forms are changed again. This is because of the replacement at runtime as you mentioned - rigth?

I also have troubles with user information inside the form. We did a domain Migration and of course within the existing infopath tasks forms there are the old user data inside. I wrote a script to update the user information in the xml structure of the existing tasks forms but i seem that my changes are replaced after a while...

So there is no database table where I see all the items from the worklist in an easy way, right?

Best Regards

Jochen 

Sad to say that you're correct on both counts.

If the XML wasn't encrypted in the database it would be easy to do, but there is no way to decrypt it except at runtime.  Not without some custom solution, which K2 does not provide (at least without using their consultancy service, anyway).